In California, Field's legal practice boomed and he was elected alcalde, a form of mayor and justice of the peace under the old Mexican rule of law, of Marysville (curiously, he was elected Alcalde just three days after his arrival in Marysville).[2] Because the Gold Rush city could not afford a jail, and it cost too much to transport prisoners to San Francisco, Field implemented[clarification needed] the whipping post, believing that without such a brutal implement many in the rough and tumble city would be hanged for minor crimes. The voters sent him to the California State Assembly in 1850 to represent Yuba County, but he lost a race the next year for the State Senate. His successful legal practice led to his election to the California Supreme Court in 1857, serving six years.[3]

During his time on the Supreme Court of California, Field had a special coat made with pockets large enough to hold two pistols so that he could shoot at his various enemies through the pockets.[4] In 1858 he was challenged to a duel by a fellow Judge (William T. Barbour) but at the dueling ground, neither man fired his gun.[5]

In 1859 Field replaced the former chief justice of the California Supreme Court, David S. Terry because Judge Terry killed a United States Senator from California (David Colbreth Broderick) in a duel and left the state.[6] Oddly, Field and Terry's paths crossed again 30 years later when Field, acting in his capacity as a judge of the 9th Federal Circuit Court, ruled against Terry in a convoluted divorce case (and had him sent to jail for contempt of court as well). Seeking revenge, Terry attempted to kill Field in 1889 near Stockton, California, but was instead shot dead by Justice Field's bodyguard, U.S. Marshal David B. Neagle (1847-1925). Ironically, legal issues arising from the killing of Mr. Terry came before the Supreme Court in the 1890 habeas corpus case of In re Neagle.[7] To no one's
surprise, the Supreme Court ruled the Attorney General of the United States had authority to appoint U.S. Marshals as bodyguards to Supreme Court Justices and Marshal Neagle had acted within the scope of his authority in shooting former Judge Terry.

On March 6, 1863, Abraham Lincoln appointed Field to the newly created tenth Supreme Court seat,[a] to achieve both regional balance (he was a Westerner) and political balance (he was a Democrat, albeit a Unionist one). The appointment would also give the court someone familiar with real estate and mining issues. Field was confirmed by the United States Senate on March 10, 1863, and received his commission the same day.

Early in his career, Field wrote opinions against California's laws discriminating against the Chinese immigrants to that state.[9] Serving as an individual jurist in district court, he notably struck down the so-called 'Pigtail Ordinance' in 1879, which was regarded as discriminating against Chinese, making him unpopular with the Californian public. However, as a member of the U.S. Supreme Court, he penned opinions infused with racist anti-Chinese-American rhetoric, most notably in his majority opinion in The Chinese Exclusion Case, Chae Chan Ping v. United States, 130 U.S. 581 (1889), and in his dissent in Chew Heong v. United States, 112 U.S. 536 (1884).

Field insisted on breaking John Marshall's record of thirty-four years on the court, even though he was not able to handle the workload. His colleagues asked him to resign due to his being intermittently senile[10] but he refused, staying on until 1897. He lived only two years more, dying in Washington, D.C., and was buried there in the Rock Creek Cemetery.[11][12]

Justice Field's aspirations to become Chief Justice went unfulfilled, as he had made many enemies both political and personal.[13] He is the second longest serving Associate Justice. Field wrote 544 opinions, more than any other justice save for Justice Samuel Miller (by comparison, Chief Justice Marshall wrote 508 opinions in his 34 years on the court).[14]

^Gorham, George C. (2005). "The Story of the Attempted Assassination of Justice Field by a Former Associate on the Supreme Bench of California". Journal of the Supreme Court Historical Society. Vol. 30 no. 2. p. 105. doi:10.1111/j.1540-5818.2005.00102.x.